Letters Early detection of psychosis

Rational policy making for early psychosis might yet become possible

BMJ 2012; 344 doi: http://dx.doi.org/10.1136/bmj.e3137 (Published 08 May 2012) Cite this as: BMJ 2012;344:e3137
  1. Anthony J Pelosi, honorary professor of psychiatry1
  1. 1Regional Eating Disorders Unit, St John’s Hospital, Livingston, West Lothian EH54 6PP, UK
  1. anthony.pelosi{at}nhs.net

On the basis of the results of previous investigations, Morrison and colleagues estimated that without active treatment 30% of their study participants with at risk mental states would later develop schizophrenia.1 However, only 9% of control subjects and 7% of those who received cognitive therapy developed a psychotic illness.

They have been warned about this lowering of the transition rate for a decade.2 3 It has occurred because, as we all know, the positive predictive value of a diagnostic test depends on the prevalence of the condition in the population to which it is applied.4 Earlier studies were conducted in people referred by consultant psychiatrists and general practitioners to specialised “prodromal” clinics; 30-70% of these patients were, indeed, developing a psychosis.5 Research assessments could predict with reasonable accuracy who would become seriously ill.

Early intervention teams then urged general practitioners to lower their referral threshold. They also encouraged primary care teams, counsellors, clergy, teachers, probation workers, housing officers, and worried families to make direct referrals. Not surprisingly, true pre-psychotic states are infrequent among such patients. Hence, assessments of at risk mental states will have a low positive predictive value. The brilliant BMJ paper by Mathers and Hodgkin in 1989, which clearly explains implications of the positive predictive value, should be required reading for all early intervention practitioners.4

I have recently gained the impression that the epidemiological and clinical errors that underpin the astonishingly influential early intervention for psychosis movement are gradually dawning on its advocates. Perhaps the spectre of “psychosis risk syndrome” or “attenuated psychotic symptoms syndrome” in the next Diagnostic and Statistical Manual of Mental Disorders has focused their minds. Hopefully this important study—combined with proper understanding of positive predictive value—will be the start of rational policy making and sensible care for people in the early stages of major mental disorders.

Notes

Cite this as: BMJ 2012;344:e3137

Footnotes

  • Competing interests: None declared.

References